Panasonic 744T - Manual (Page 56)

744T User Guide and Technical Information
54
firmware v. 1.04 Features and specifications are subject to change. Visit www.sounddevices.com for the latest documentation.
Recording Time Calculation
The calculation of available 744T recording time involves three factors:
• track count - how many concurrent audio tracks are selected for recording.
• data rate - calculated from the sample rate and bit depth for non-compressed audio and by bit
rate for data compressed audio. Data rate determines how big the data “container” is for the
audio signal (see the calculation below for determining PCM audio).
• storage medium capacity - typically expressed in GB
Uncompressed Recording Time in Track-Hours
Data Rate (bit depth/sample rate), one track
16/44.1
(5.05 MB/min)
16/48
(5.49 MB/min)
24/48
(8.24 MB/min)
24/96
(16.5 MB/min)
24/192
(33.0 MB/min)
Stora
g
e
in GB
(1000 MB = 1 GB)
1 3.30 3.03 2.02 1.01 0.51
2 6.60 6.07 4.05 2.02 1.01
4 13.2 12.1 8.09 4.05 2.02
8 26.4 24.3 16.2 8.09 4.05
15 49.5 45.5 30.3 15.2 7.59
40 132 121 80.9 40.5 20.2
60 198 182 121 60.7 30.3
100 330 303 202 101 50.6
The chart above shows recording time available with the 744T. Time is expressed in hours per track
(track-hours) at the specifi ed data rate supported by the 744T. If recording two tracks, divide the
track hours fi gure by two. Similarly for four-track recording, divide track-hours by four. Note that
the 744T supports additional sample rate / bit depth combinations, however, only the most common
are included below.
Record Time
The chart shows that when recording 24-bit/48 kHz audio to a 40 GB hard drive the maximum
amount of recording time available roughly 80 track-hours. If recording a stereo two-track fi le, this
yields 40 stereo hours of record time.
Note that most storage mediums now quote capacity in GB using SI units, where 1000 megabytes
equals one gigabyte.
PCM Audio
Uncompressed digital audio is expressed numerically by two measurements, bit depth and sampling
frequency, such as 16-bit/48 kHz. These two numbers are used to compute the data rate of uncom-
pressed audio.
Audio Data Rate = Bit Depth x Sampling Frequency
In the example below the data rate of a single 16-bit/48 kHz audio stream is computed in megabytes
per minute. Division by 1,048,576 converts from bits to megabits. Division by 8 converts from mega-
bits to megabytes; multiply by 60 converts seconds to minutes.
(((16 x 48000) / 1,048,576) / 8) x 60 = 5.49 MB/min